I had a chance last night to capture the remaining data for NGC7000 The North America nebula, I needed at least 20 images each using the Baader OIII and SII filters to go with the Ha data I had already captured. The conditions were not perfect as there was patchy cloud drifting across most of the time, so I had to work between the clouds as they cleared the patch of sky I was aiming at. As a result I threw away a lot of images as they were not good enough for stacking together ( especially the SII images, I think next time I’ll have to do longer exposures with this filter ) so it took longer to get all the data than it would had the sky been clear. Interestingly being so close to full, the 82% illuminated moon had no adverse impact using the narrow band filters I’m not sure what it would be like imaging an object near to the moon when full, I’ll have to find out. ( I’m sure imaging with the Red, Green and Blue filters under such a bright moon would be awful ) . After stacking and processing the data I was left with three narrow band images to combine in PhotoShop cs5. Due to a misalignment in camera position between the Ha data previously captured and the OIII, SII data caught last night the images had to be rotated slightly to line up with the Ha image.
I allocated the images in the colour channels in the following order.
Ha – Green, OIII – Blue, SII – Red.
Then adjusted the selective colour to give me the sythesised Hubble Palette, and adjusted the saturation slightly and did some noise reduction too.
For a first attempt at this I’m quite pleased with the results, I’m going to have to write down what I did for repeatability in the future.